This is very useful to prevent compiler noise about invalid cflags; particularly
for the -mms-bitfields cflag which most libraries send to the mingw-gcc
compiler. More can be added later.
Instead of checking if we're on Windows and not even trying, try to symlink and
if that fails due to insufficient privileges, then just continue. This allows
people who know what they're doing to allow users other than Administrators to
make symlinks on Windows, or allows them to just run Meson as an Administrator.
Jussi Pakkanen